1. Field of the Invention
The invention relates to a diagnostic device for a multi-antenna arrangement with a diversity processor.
2. The Prior Art
When testing active and passive components of a mobile receiver installation, for example a radio receiver, multi-antenna arrangements with antenna diversity are problematic due to differentiated testing of the individual antenna and the condition of the antenna's electrical connections to the radio receiver. In addition, the interfaces available for the tie-up for measuring and testing systems are difficult to access and require extensive dismantling work. It is difficult to determine which antenna is connected at the given time, due to the switching position of the antenna diversities. Antenna determination can not be achieved by measurements of the receiving level on the antenna connection box of the radio receiver because the signal level falls short of a defined preset value in diversity systems. Therefore, the radio receiver is automatically switched via a change-over switch to one of the other antennas where an adequate reception level can be detected.
A circuit arrangement for testing the function of mobile radio reception installations is known from European Patent EP 0 806 849 A2, which can be used with diversity systems as well. This invention discloses a high-frequency signal that is generated by the circuit on the output side. The HF-signal substantially corresponds with the adjusted receiver frequency of the radio receiver and is coupled in via the receiver antenna, whereby the level of the received signal is measured. A switching signal generator is used to sequentially step the antenna switch of a diversity processor. This allows the high-frequency signal to be coupled in by different antennas of the diversity system, and the received power of the individual antenna can be measured. However, this system does not provide a defined starting condition for beginning the function test.
Another circuit arrangement for testing multi-antenna systems is described in German Patent DE 195 13 872 A1. This invention describes an antenna-specific pulse sequence, which is generated either indirectly by the radio receiver, an external testing device, or a special converter circuit, and the change-over switch of the antenna diversity system is switched through to the radio receiver according to the pulse sequence. The pulse sequence can be fed into the diversity system either by the antenna cable or an intermediate frequency output of the radio receiver. The intermediate arrangement of filters separates the test pulses from the main signals transmitted by the lines. A test signal is subsequently transmitted on the same channel, and the receiver conditions of the individual antenna can then be tested by the test signal.
It is essential to this system to intervene with or make changes on the circuitry that relate to the diversity system and/or the radio receiver. Consequently, these systems are not suitable for testing existing radio receiver installations with antenna diversity systems.